Induction-coil for telephone service



(No Model.)

B. B. HAMLIN.

INDUCTION COIL FOR TELEPHONE SERVIGE. No. 350,130. Patented Oct. 5,1886.

Nv PETERS. Pnom-ump m hor, wmhin mn, D. c.

UNITED STATES PATENT QFFIGE.

EVELYN l3. IIAMLIN, OF CHICAGO, ILIiINOlS.

INDUCTION-COIL FOR TELEPHONE SERVICE.

SPECIFICATION forming part; of Letters Patent No. 350,130, dated October5, 1886. Application tiled May 1, 1886. Serial X0. 200,773. (No model.)

To (LZZ whom it may concern:

Be it known that I, EVELYN B. HAMLIN, ot' Chicago, in the county of Cookand State of Illinois,havc invented a ,ncw, useful, and ImprovedImluction-Coil for Telephone Service, ol' which the following is adescription, reference being had to the accompanying drawings, in which-Figure l is a side view of my i1n rovcd coil, a portion of the samebeing shown. in section and broken away in order to show the differentwindings, and Fig. 2 is a central longitudinal sectional View showingthe manner of constructing said coil, together with an outline ordiagram of the connections of the respective sub-coils with thetelephone service.

Li kc letters of reterencc indicate like parts in the different figures.

The object of my invention is to so construct an induction-coil fortelephonic service that the current from a local battery may be utilizedto induce a line-current upon a secondary or sub coil, and to amplify alocal induced current in a third sub-coil, whereby I am enabled toeliminate the usual objectionable etl'ccts upon the receiving-instrnmeutot' line-imluetion, all ot which is hereinafter more particular] ydescribed and claimed.

My improved imluction-coil consists of tour distinct windings or coils,the first and fourth of which are connected and are of low resistance,and the second and third of which are independent and of highresistance. The fourth. is a continuation of the first, the two (firstand l'ourth) being in direct circuit with a battery. Instead ofdescribing these as first, second, third, and t'onrth, or primary,secondary, &c., I prefer to describe them as primary, (first) primaryinduction, (second,) secondary induction, t-llll'tl,) and primaryextension, (fourth) In the drawings, A, Fig. 1, represents an ordinaryinsnlatingspool surrounding the usual sottiron core, B. I first windupon said spool a primary coil, 0, of large insulated wire, and then,suspending said winding, I place over said primary coil (3 aprimary-induction winding or coil, 1), of tine insulated wire, theterminals (Z d, Fig. 2, of which preferably connect, respectively, withthe line D and ground 13". Around said primary-i nduetion winding Iplace a sccondary-induction coil, E, of like or varying resistance tothat of said primaryinduction coil, but preterably the same, theterminals 0 e of which maybe connected with an ordinaryllltlgllQtO'JTOCOIVOT, F, as shown in Fig. 2, thus 'torming a localcircuit therewith. Around said coil E, I then continue the wind ing ofsaid primary coil. 0, thus forming a primary extension,(). Theconvolutions ol'all. of said coils are in the same direction, and theterminals 0 0, respectively, of said primary and primary-extension coilsare connected with the binding-posts g r/ of a transmitting-instrument,G, in circuit with which a local battery, H, is interposed. Theinfluence of a passing current through the primary coil C induces acurrent upon the coil D and line D the return of which forms a localinduced current upon the coil E in circuit, as stated, with the receiverF, the action of which local induced current is in turn amplified by thelocal-battery current upon the primary-extension coil 0. By this systemof coils, and by thus placing the receiver, I am enabled to overcomecertain difficulties and objections incident to the placing of saidreceiver directly in circuit with the line-wire. The disturbances whichresult from line-induction are largely avoided, while the sounds fromthe transmitting-instrtc ment are thus rendered clearer and moredistinct.

Having thus described my invent ion, what I claim, and desire to secureby Letters Patent, 1s-

1. An induction -coil consisting ot' a primary coil ot'coarse wi resurrounding a sot't-iron core, a primary-induction coil of line wire,the terminals of which are designed to be connected with the line andground, respectively, a continuous secondary-induction coil of linewire, with the terminals of which a local circuit may be formed, and aprimaryextension coil of coarse wire connected with said primary coiland surrounding the whole, the terminals of said primary andprin'iary-extension coils being intended to be in circuit with a localbattery, substantially as and for the purposes set forth.

2. In an induction-coil having the core 13, the primary coil 0, the coilD, connected with the line and ground, respectively, primary-extensioncoil 0, connected with said primary coil, and the interposed coil E,arranged substantially as and for the purposes set forth.

3. The combination, in an induction-e0il,of asoft-iron core, aprimarycoil of low resistance, continuous and independent primary and secondaryinduction coils of high resistance, and a primary-extension coilsurrounding the whole and connected with said primary coil,substantially as and for the purposes set forth.

4. In a telephone service, an induction-coil consisting of a primarycoil of coarse wire en- Veloping a soft-iron core, a primary-inductioncoil of fine wire having its terminals connected with a telephone-lineand with the ground, re-

EVELYN B. HAMLIN.

WVitnesses:

MARTIN M. GRIDLEY, JOHN S. THOMPSON.

